SPCs are built with a clear housing on one side. This allows a user to confirm that they are wired correctly before connecting them. On some older female pin receptacles, the electrical contacts are not deeply recessed in the plug body and can easily be accidentally contacted resulting in an electric shock if the circuit is live. This was one advantage of the Edison outlet in that it was impossible to contact live parts unless something conductive was inserted into the slots. New connectors have the contacts deeper inside the body. A major disadvantage to this style of connector is that it can be mated with one connector reversed, reversing ground and line connections. For equipment mechanically attached to grounded building structures such as a lighting instrument mounted to a batten or grid this will cause a line-ground short circuit. For equipment not attached to a building ground, such as a floor-mounted lighting instrument, this condition will cause the chassis of the equipment to become electrified creating a shock hazard. Care must therefore be taken to avoid misaligning plugs. It is also possible to mate stage pin connectors such that the ground pin is inserted into the neutral socket and the neutral pin is inserted into the ground socket, but this mistake does not usually result in a fault condition unless there is a hot-neutral reverse upstream in the cabling. Standards Stage pin connectors are specified by Entertainment Services and Technology Association (ESTA) standard"ANSI E1.24 – 2012 (R2017) Entertainment Technology Dimensional Requirements for Stage Pin Connectors" Other connectors used in theatre applications Many theatres also use NEMA connectors, which are the standard connector used in homes and businesses in North America, because of their availability and the ability to connect household fixtures to a theatrical control system. Twist-lock connectors are used in many theatres because of their locking feature, which will not allow fixtures to become accidentally disconnected. Connectors used to power lighting fixtures must be rated at 20 amperes or higher, depending on local electrical codes. Temporary high-power distribution wiring often employs camlock connectors to connect dimming equipment, power distribution units, controllers for motorized chain hoists, and other high-power equipment to a company switch, generator, or other tie-in point. For individual dimmable lighting fixtures, UK theatrical lighting installations normally use the BS 546 type plug rated at 15 A (the higher phase voltage of 230 V allows lower currents